Hepatitis B and C serologic profiles of Canadian organ donors and recipients: retrospective 10-year review at a single center.

BACKGROUND: Hepatitis C virus (HBV) and hepatitis C virus (HCV) are important causes of hepatitis and can be transmitted from organ donor to recipient. This study aimed to determine HBV and HCV serologic profiles of a population of Canadian solid organ transplant (SOT) donors and recipients, including prevalence of recipient HBV immunity. METHODS: Data on age, gender, organ transplanted, and pre-transplant HBV and HCV serology for SOT donors and recipients at a Canadian hospital from 2001 to 2011 were obtained from a transplant database. RESULTS: There were 2455 recipients (2205 adults, 250 children), and 1559 donors. Over 50% of adult and 44% of pediatric recipients were HBV non-immune pre-transplant. Pediatric recipients were more likely to have HBV vaccine immunity than were adult recipients (48.8% vs. 28.9%, P < 0.001). Prevalence of HBV vaccine immunity was highest in renal recipients (48.3% in adult, 63.2% in pediatric recipients). Recipient HBV vaccine immunity increased from 5.8% in 2001 to 44.5% in 2011 (P < 0.001). Of 134 adult recipients with prior HBV infection, 59 (44%) were co-infected with HCV. Only 0.6% of adult non-liver recipients had acute or chronic HBV infection and 3.2% were anti-HCV positive. Only 2 donors had acute or chronic HBV infection, 29 had prior HBV infection, 9 were isolated hepatitis B core antibody positive, and 15 were anti-HCV positive. CONCLUSIONS: The prevalence of HBV vaccine immunity in SOT candidates is low, but increased from 2001 to 2011. Opportunities for quality improvement in pre-transplant HBV immunization exist. HCV co-infection is common in recipients with prior HBV infection. Prevalence of HCV infection in non-liver transplant recipients is low.

Commutability of the First World Health Organization International Standard for Human Cytomegalovirus.

Quantitative detection of cytomegalovirus (CMV) DNA has become a standard part of care for many groups of immunocompromised patients; recent development of the first WHO international standard for human CMV DNA has raised hopes of reducing interlaboratory variability of results. Commutability of reference material has been shown to be necessary if such material is to reduce variability among laboratories. Here we evaluated the commutability of the WHO standard using 10 different real-time quantitative CMV PCR assays run by eight different laboratories. Test panels, including aliquots of 50 patient samples (40 positive samples and 10 negative samples) and lyophilized CMV standard, were run, with each testing center using its own quantitative calibrators, reagents, and nucleic acid extraction methods. Commutability was assessed both on a pairwise basis and over the entire group of assays, using linear regression and correspondence analyses. Commutability of the WHO material differed among the tests that were evaluated, and these differences appeared to vary depending on the method of statistical analysis used and the cohort of assays included in the analysis. Depending on the methodology used, the WHO material showed poor or absent commutability with up to 50% of assays. Determination of commutability may require a multifaceted approach; the lack of commutability seen when using the WHO standard with several of the assays here suggests that further work is needed to bring us toward true consensus.

Multicenter evaluation of a commercial cytomegalovirus quantitative standard: effects of commutability on interlaboratory concordance.

Commutability of quantitative reference materials has proven important for reliable and accurate results in clinical chemistry. As international reference standards and commercially produced calibration material have become available to address the variability of viral load assays, the degree to which such materials are commutable and the effect of commutability on assay concordance have been questioned. To investigate this, 60 archived clinical plasma samples, which previously tested positive for cytomegalovirus (CMV), were retested by five different laboratories, each using a different quantitative CMV PCR assay. Results from each laboratory were calibrated both with lab-specific quantitative CMV standards ("lab standards") and with common, commercially available standards ("CMV panel"). Pairwise analyses among laboratories were performed using mean results from each clinical sample, calibrated first with lab standards and then with the CMV panel. Commutability of the CMV panel was determined based on difference plots for each laboratory pair showing plotted values of standards that were within the 95% prediction intervals for the clinical specimens. Commutability was demonstrated for 6 of 10 laboratory pairs using the CMV panel. In half of these pairs, use of the CMV panel improved quantitative agreement compared to use of lab standards. Two of four laboratory pairs for which the CMV panel was noncommutable showed reduced quantitative agreement when that panel was used as a common calibrator. Commutability of calibration material varies across different quantitative PCR methods. Use of a common, commutable quantitative standard can improve agreement across different assays; use of a noncommutable calibrator can reduce agreement among laboratories.

Circulating antibody free light chains and risk of posttransplant lymphoproliferative disorder.

Posttransplant lymphoproliferative disorder (PTLD) is a major complication of solid-organ transplantation. With human immunodeficiency virus infection (an analogous immunosuppressive state), elevated kappa and lambda immunoglobulin free light chains (FLCs) in peripheral blood are associated with increased risk of lymphoma. To assess the role of B-cell dysfunction in PTLD, we measured circulating FLCs among Canadian transplant recipients, including 29 individuals with PTLD and 57 matched transplant recipients who were PTLD-free. Compared with controls, PTLD cases had higher kappa FLCs (median 1.53 vs. 1.07 times upper limit of normal) and lambda FLCs (1.03 vs. 0.68). Using samples obtained on average 3.5 months before PTLD diagnosis, cases were more likely to have polyclonal FLC elevations (i.e. elevated kappa and/or lambda with normal kappa/lambda ratio: odds ratio [OR] 4.2, 95%CI 1.1-15) or monoclonal elevations (elevated kappa and/or lambda with abnormal ratio: OR 3.0, 95%CI 0.5-18). Strong FLC-PTLD associations were also observed at diagnosis/selection. Among recipients with Epstein-Barr virus (EBV) DNA measured in blood, EBV DNAemia was associated with FLC abnormalities (ORs 6.2 and 3.2 for monoclonal and polyclonal elevations). FLC elevations are common in transplant recipients and associated with heightened PTLD risk. FLCs likely reflect B-cell dysfunction, perhaps related to EBV-driven lymphoproliferation.

Factors associated with vaccine failure and vertical transmission of hepatitis B among a cohort of Canadian mothers and infants.

Mother-to-child transmission of hepatitis B virus (HBV) continues to occur despite immunoprophylaxis. We examined maternal factors contributing to transmission in infants receiving adequate immunoprophylaxis in Alberta, Canada. Prenatal specimens from HBsAg-positive women whose babies developed HBV infection despite immunoprophylaxis (cases) and HBsAg-positive mothers whose babies did not (controls) were tested for HBsAg, HBeAg and HBV DNA. Specimens with detectable DNA underwent HBV genotyping. Routinely collected surveillance data and laboratory test results were compared between cases and controls. Twelve cases and 52 controls were selected from a provincial registry from 2000 to 2005. At the time of prenatal screening, median maternal age was 31 years [interquartile range (IQR): 27.5-34.5], and median gestational age was 12 weeks (IQR 10.0-15.5). Cases were more likely than controls to test positive for HBeAg (77.8% vs. 23.1%; P < 0.05). Of all mothers with detectable viral load (n = 51), cases had a significantly higher median viral load than did controls (5.6 × 10(8) IU/mL vs. 1750 IU/mL, P < 0.0001). Of the two cases who were HBeAg negative, one had an undetectable viral load 8 months prior to delivery and a sP120T mutation. The viral load in the other case was 14,000 IU/mL. The majority of isolates were genotype B (31.3%) and C (31.3%) with no significant differences in genotype between cases or controls. In this case-control study, transmission of HBV to infants was more likely to occur in mothers positive for HBeAg and with high HBV DNA.

Nucleic acid testing (NAT) of organ donors: is the 'best' test the right test? A consensus conference report.

Nucleic acid testing (NAT) for HIV, HBV and HCV shortens the time between infection and detection by available testing. A group of experts was selected to develop recommendations for the use of NAT in the HIV/HBV/HCV screening of potential organ donors. The rapid turnaround times needed for donor testing and the risk of death while awaiting transplantation make organ donor screening different from screening blood-or tissue donors. In donors with no identified risk factors, there is insufficient evidence to recommend routine NAT, as the benefits of NAT may not outweigh the disadvantages of NAT especially when false-positive results can lead to loss of donor organs. For donors with identified behavioral risk factors, NAT should be considered to reduce the risk of transmission and increase organ utilization. Informed consent balancing the risks of donor-derived infection against the risk of remaining on the waiting list should be obtained at the time of candidate listing and again at the time of organ offer. In conclusion, there is insufficient evidence to recommend universal prospective screening of organ donors for HIV, HCV and HBV using current NAT platforms. Further study of viral screening modalities may reduce disease transmission risk without excessive donor loss.

Cell-mediated immunity to predict cytomegalovirus disease in high-risk solid organ transplant recipients.

Late-onset cytomegalovirus (CMV) disease commonly occurs after discontinuation of antiviral prophylaxis. We determined the utility of testing CD8+ T-cell response against CMV as a predictor of late-onset CMV disease after a standard course of antiviral prophylaxis. Transplant patients at high-risk for CMV disease were enrolled. CD8+ T-cell-mediated immunity (CMI) was tested using the QuantiFERON-CMV assay at baseline, 1, 2 and 3 months posttransplant by measurement of interferon-gamma response to whole blood stimulation with a 21-peptide pool. The primary outcome was the ability of CMI testing to predict CMV disease in the first 6 months posttransplant. There were 108 evaluable patients (D+/R+ n = 39; D-/R+ n = 34; D+/R- n = 35) of whom 18 (16.7%) developed symptomatic CMV disease. At the end of prophylaxis, CMI was detectable in 38/108 (35.2%) patients (cutoff 0.1 IU/mL interferon-gamma). CMV disease occurred in 2/38 (5.3%) patients with a detectable interferon-gamma response versus 16/70 (22.9%) patients with a negative response; p = 0.038. In the subgroup of D+/R- patients, CMV disease occurred in 1/10 (10.0%) patients with a detectable interferon-gamma response (cutoff 0.1 IU/mL) versus 10/25 (40.0%) patients with a negative CMI, p = 0.12. Monitoring of CMI may be useful for predicting late-onset CMV disease.

Interlaboratory comparison of cytomegalovirus viral load assays.

To assess interlaboratory variability in qualitative and quantitative cytomegalovirus (CMV) viral load (VL) testing, we distributed a panel of samples to 33 laboratories in the USA, Canada and Europe who performed testing using commercial reagents (n = 17) or laboratory-developed assays (n = 18). The panel included two negatives, seven samples constructed from purified CMV nucleocapsids in plasma (2.0-6.0 log(10) copies/mL) and three clinical plasma samples. Interlaboratory variation was observed in both actual (range, 2.0-4.0 log(10) copies/mL) and self-reported lower limits of detection (range, 1.0-4.0 log(10) copies/mL). Variation observed in reported results for individual samples ranged from 2.0 log(10) (minimum) to 4.3 log(10) (maximum)(.) Variation was greatest at low VLs. Assuming +/- 0.5 log(10) relative to the expected result represents an acceptable result, 57.6% of results fell within this range. Use of commercially available reagents and procedures was associated with less variability compared with laboratory-developed assays. Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). The significant interlaboratory variability in CMV VL observed may be impacting patient care and limiting interinstitutional comparisons. The creation of an international reference standard for CMV VL assay calibration would be an important step in quality improvement of this laboratory tool.

Interlaboratory comparison of epstein-barr virus viral load assays.

To assess interlaboratory variability in qualitative and quantitative Epstein-Barr virus (EBV) viral load (VL) testing, we distributed a panel of samples to 28 laboratories in the USA, Canada and Europe who performed testing using commercially available reagents (n = 12) or laboratory-developed assays (n = 18). The panel included two negatives, seven constructed samples using Namalwa and Molt-3 cell lines diluted in plasma (1.30-5.30 log(10) copies/mL) and three clinical plasma samples. Significant interlaboratory variation was observed for both actual (range 1.30-4.30 log(10) copies/mL) and self-reported (range, 1.70-3.30 log(10) copies/mL) lower limits of detection. The variation observed in reported results on individual samples ranged from 2.28 log(10) (minimum) to 4.14 log(10) (maximum). Variation was independent of dynamic range and use of commercial versus laboratory-developed assays. Overall, only 47.0% of all results fell within acceptable standards of variation: defined as the expected result +/- 0.50 log(10). Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). Kinetics of change in VL appears more relevant than absolute values and clinicians should understand the uncertainty associated with absolute VL values at their institutions. The creation of an international reference standard for EBV VL assay calibration would be an initial important step in quality improvement of this laboratory tool.

Comparison of quantiferon-TB gold with tuberculin skin test for detecting latent tuberculosis infection prior to liver transplantation.

Screening for latent tuberculosis infection (LTBI) is recommended prior to organ transplantation. The Quantiferon-TB Gold assay (QFT-G) may be more accurate than the tuberculin skin test (TST) in the detection of LTBI. We prospectively compared the results of QFT-G to TST in patients with chronic liver disease awaiting transplantation. Patients were screened for LTBI with both the QFT-G test and a TST. Concordance between test results and predictors of a discordant result were determined. Of the 153 evaluable patients, 37 (24.2%) had a positive TST and 34 (22.2%) had a positive QFT-G. Overall agreement between tests was 85.1% (kappa= 0.60, p < 0.0001). Discordant test results were seen in 12 TST positive/QFT-G negative patients and in 9 TST negative/QFT-G positive patients. Prior BCG vaccination was not associated with discordant test results. Twelve patients (7.8%), all with a negative TST, had an indeterminate result of the QFT-G and this was more likely in patients with a low lymphocyte count (p = 0.01) and a high MELD score (p = 0.001). In patients awaiting liver transplantation, both the TST and QFT-G were comparable for the diagnosis of LTBI with reasonable concordance between tests. Indeterminate QFT-G result was more likely in those with more advanced liver disease.

Trends in testing behaviours for hepatitis C virus infection and associated determinants: results from population-based laboratory surveillance in Alberta, Canada (1998-2001).

Little is currently known about hepatitis C virus (HCV) test seeking behaviours at the population level. Given the centralized nature of testing for HCV infection in the province of Alberta, Canada, we had an opportunity to examine HCV testing behaviour at the population level on all newly diagnosed HCV-positive cases using laboratory data to validate the time and number of prior tests for each case. Record linkage identified 3323, 2937, 2660 and 2703 newly diagnosed cases of HCV infections in Alberta during 1998, 1999, 2000 and 2001, respectively, corresponding to age-adjusted rates of 149.8, 129, 114.3 and 113.7 per 100,000 population during these years, respectively. Results from secondary analyses of laboratory data suggest that the majority of HCV cases (95.3%) who were newly diagnosed between 1998 and 2001 were first-time testers for HCV infection. Among repeat testers, analysis of a negative test result within 1 year prior to a first of a positive test report suggests that 211 (38.4%) may be seroconvertors. These findings suggest that 339 or 61.7% of repeat testers may not have discovered their serostatus within 1 year of infection. Among this group, HCV testing was sought infrequently, with a median interval of 2.3 years between the last negative and first positive test. This finding is of concern given the risks for HCV transmission, particularly if risk-taking behaviours are not reduced because of unknown serostatus. These findings also reinforce the need to make the most of each test-seeking event with proper counselling and other appropriate support services.

Prevalence and estimated incidence of blood-borne viral pathogen infection in organ and tissue donors from northern Alberta.

To determine the potential safety benefit of introducing nucleic acid testing (NAT) in tissue and organ donors, the risk of virus transmission was examined in a Canadian population. Anonymous data on Northern Alberta tissue and organ donors from 1998 to 2004 were used to determine the seroprevalence and estimate the seroincidence and residual risk of HIV, HBV, HCV and HTLV infection. Of the 3372 donors identified, 71.1% were surgical bone, 13.2% were living organ and 15.6% were deceased organ/tissue donors. Seroprevalence was: HIV 0.00%, HBV 0.09%, HCV 0.48% and HTLV 0.03%. Incidence (/100,000 p-yrs) and residual risks (/100,000 donors) could only be estimated for HBV (24.2 and 3.9) and HCV (11.2 and 2.2). Risk estimates were higher for deceased donors than surgical bone donors. HCV had the highest prevalence and HBV had the highest estimated incidence. HIV and HTLV risks were extremely low precluding accurate quantification. In this region of low overall viral prevalence, HCV NAT would be most effective in deceased organ donors. In surgical bone donors the cost of implementing NAT is high without significant added safety benefit.

A review of general hepatitis C virus lookbacks in Canada.

BACKGROUND AND OBJECTIVES: This article reviews the Canadian experience with general hepatitis C virus (HCV) lookback programmes. MATERIALS AND METHODS: Comprehensive literature searches were conducted in PubMed, Medline, HealthSTAR and EMBASE. In addition, bibliographic searches were performed on all retrieved articles, and provinces were contacted to determine whether they had performed general HCV lookbacks. RESULTS: Of the seven Canadian general HCV lookbacks identified, two focused specifically on the paediatric population. The proportion of transfused patients presumed to be alive varied from 48.9 to 97.5%. Between 55.3 and 99.1% of letters were successfully delivered. The proportion of patients tested for HCV and subsequently found to be HCV positive varied considerably (66.2-80.4% and 0.9-5.0%, respectively). Newly diagnosed patients represented 42-58% of cases identified. CONCLUSIONS: The Canadian general HCV lookback experience successfully identified previously undiagnosed HCV-positive patients, but the resources required to notify patients are high and the yield is relatively low. The effectiveness may be greatest in the paediatric population.

Diagnosis and management of posttransplant lymphoproliferative disorder in solid-organ transplant recipients.

The Epstein-Barr virus (EBV) has a pivotal pathophysiologic role in the development of most lymphoproliferative disorders that occur after solid-organ transplantation. The term "EBV-associated posttransplant lymphoproliferative disorder" (PTLD) includes all clinical syndromes of EBV-associated lymphoproliferation, ranging from uncomplicated posttransplant infectious mononucleosis to true malignancies that contain clonal chromosomal abnormalities. PTLDs are historically associated with a high mortality rate in patients who have a monoclonal form of the disorder. Recently described approaches to pathology, diagnosis, treatment, and preventive strategies of PTLD, however, have the potential to improve outcome.

Recurrent Epstein-Barr virus associated disease in a cardiac transplant patient: evolution from plasmacytic hyperplasia to diffuse large cell lymphoma.

An Epstein-Barr virus (EBV)-seronegative 31-year-old male underwent cardiac transplantation in 1991 for congenital cardiomyopathy. He presented with a protracted course of waxing and waning lymphadenopathy beginning four years after transplantation with eventual progression to a fulminant EBV-positive large cell lymphoma eight years after transplantation. Risk factors for the development of post-transplant lymphoproliferative disease in this patient, the importance of a standardized approach to pathology in assessing therapeutic options, and the management strategies used are discussed.